Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 27, 1950 an'rromau'rs FOB mam OIL LUBRI- CANTS AND (IOMPGSITIONS CONTAINING THE SAME Herschel G. Smith, Wallingford, and Troy L. Cantrell, Lansdowne, Pa., and John G. Peters, Audubon, N. 3., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application January 4, 1949, Serial No. 69,234

16 Claims. (Cl. 252-51.5)

This invention relates to antioxidants for mineral oil lubricants and compositions containing the same, and more particularly, it relates to addition agents for mineral oil lubricants which inhibit the oxidative deterioration of said lubricants.

- In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is due at least in part to oxidation effects on mineral lubricating oils. In turbine oils the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubricants which will inhibit the oxidative deterioration of such lubricants.

It is a further object of this invention to provide improved mineral oil lubricant compositions which are stable against oxidation under service conditions.

These and other objects are accomplished by the present invention wherein an addition agent for mineral oil lubricants is prepared by condensing dimethoxybenzaldehyde, N-dimethylaniline and formaldehyde in the presence of an activated clay as a catalyst, and-recovering the condensation product. The condensation product so obtained in a light-colored product which, when added to mineral oil lubricants, confers good stability against deterioration by oxidation. Such condensation products and the mineral oil lubricant compositions containing them are believed to be novel and are considered parts of our invention. Contrary to what may be expected from the nature of the reactants, we do not obtain highly condensed, insoluble resinous products. On the contrary, when the above reactants are condensed in accordance with our invention, there are obtained light-colored condensation products 2 which are non-resinous and which are readily soluble in mineral oils.

In performing the condensation, the reactants are mixed and heated to a maximum temperature of 350 F. We have found that if the temperature of 350 F. is exceeded to any substantial extent, the condensation product for-med tends to be resinous and insoluble. In general, the preferred temperature for the condensation ranges from to 300 F.

The proportions of the reactants vary over a fairly wide range. The dimethoxybenzaldehyde is employed in an amount of from 1 to 2 mols, N-dimethylaniline in an amount of from 2 to 8 mols, and formaldehyde in an amount of from 2 to 8 mols. Ordinarily, it is preferred to use from 5 to 10 per cent by weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as 1 per cent by weight, and larger amounts, as high as 20 per cent by weight, may also be employed; but larger amounts than about 10 per cent by weight are ordinarily not necessary.

Any of the isomeric dimethoxybenzaldehydes or mixtures thereof may be used in accordance with our invention. These include 2,3-dimethoxybenzaldehyde, 3,4 dimethoxybenzaldehyde (veratraldehyde) and 2,4-dimethoxybenzaldehyde.

In lieu of formaldehyde, any formaldehydeyielding compound, such as parafor-maldehyde, dioxymethylene and trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term "formaldehyde" is intended to include formaldehyde-yielding compounds as well as formaldehyde itself.

Various activated clays may be employed as catalysts in accordance with our invention. Such materials are well known in the art and comprise a natural clay, such as bentonite, fullers earth fioridin and smectite, which has been acid treated These materials in order to activate the clay. are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the retants and catalysts are placed into a reaction vessel which is then closed and the mixture heated with agitation under reflux until all of the formaldehyde or formaldehyde-yielding compound has been consumed. At this time, the water which is formed as a result of the condensation is removed, preferably under vacuum, and the dehydrated condensation product is then filtered to remove the activated clay catalyst. In some instances, it is desirable to prepare our new addition agent in a concentrate in a mineral lubricating oil which ma then be diluted down with additional oil to the concentration desired in the final lubricating composition. In such instances, the mineral lubricating oil may be added in a suitable amount, say in a weight equal to the weight of reactants, to the reaction mixture in the reaction vessel, and the condensation product obtained will then be a concentrated solution of the addition agent in the mineral lubricating oil.

' The condensation products obtained in accordance with our invention are liquids or crystalline solids. While the exact nature of the chemical composition of the condensation products is unknown, all of the three reactants enter into a final unitary product. The exact manner in which the catalyst influences the reaction is unknown. However, regardless of any theory involved, the use of an activated clay catalyst is an essential feature of our invention, since if the catalyst is omitted, black, insoluble, resinous condensation products are obtained.

The following examples illustrate the preparation of our new addition agent:

Example I.Into an enamel lined reaction vessey, there .was introduced 1 mol of 2,3-dimethoxybenzaldehyde (E. K. Co. practical, M. P. 4250 C.) (166 parts by weight), 2 mols of N-dimethylaniline (242 parts by weight) and 2 mols of formaldehyde in a 37 per cent by weight aqueous solution (162 parts by, weight). To this mixture, there was added 40parts by weightof Filtrol (an activated montmorillonite). The vessel was closed and attached to a reflux condenser. The mixture was then heated to 210 F. and refluxed for 5 hours. The condensation product was then dried by distilling off all water, both that added with the formaldehyde and formed in the reaction, by heating at 280 F. The product was then filtered. It had the following properties:

.Gravity, 'A. P. I 0.8 Color, N. P. A 7.5 Neutralization No 1.08

Example II.-Example I was repeated using 1 mol of 2,3-dimethoxybenzaldehyde, 3 mols of N- dimethylaniline, 3 mole of formaldehyde and about 5 per cent by weight of an activated clay. The filtered product had the following properties:

Gravity, A. -P. I 1.2 Color, N. P. A 7.5 Neutralization N0 0.8

Gravity, A. P. I 1.1 Color, N. P. A 4.5 Neutralization No 0.6

The condensation products obtained in accordance with the above disclosures from 11- thenic or mixed base mineral oils and can be blended with mineral oils in high proportions to form concentrated solutions thereof, which may then be diluted down to'the proportions desired in the final mineral oil lubricant composition. As stated, our new addition agents are very eil'ective in inhibiting the oxidative deterioration of min-- eral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally sufiiclent. For example, our addition agents may be added to mineral lubricating oils inminor amounts, say from 0.001 to 1 per cent by weight on the mineral oil', sumcient to inhibit the oxidative deterioration of the oil. Larger amounts of our new addition agents may be used if desired but it is ordinarily unnecessary to do so.

The following examples illustrate the antioxidant eifects of our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subjected to a standard oxidation test which measures the stability of the oils to oxidation The oxidation te'streferred to is a standard test designated A. S. T. M. D943-47T. Briefly, the

test comprises subjecting the oil sample to oxygen at a temperature of 95 C. (203 F.) in the presence of water and an iron-copper catalyst. and determining the time required to build up a neutralization number of 2. The flow of oxygen is maintained at 3 liters per hour. The remarkably 'efiectlve stability to oxidation of mineral oil lubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example IV.-An improved steam turbine oil was prepared by treating a turbine oil base stock with 0.5 per cent by weight of an additive prepared according to Example I. A comparison of the properties of the base oil and improved turbine oil showed the following:

Base Oil Improved Oil Gravity, API Viscosity. SUV: 210 F Color, NPA Oxidation Test, ASIM DOB-471 113 F., 3 L. Oxygen/Hr; 4 Time Oxidized, Hrs Neutralization No of the base oil and the improved oil showed:

Base Oil Improved on Gravity, API 2s. 1s 2s. a Viscosity, SUV: 210 F..- 49. 5 49.3 Color, NPA 2. 2s 2. 25 Oxidation Test, ASTM DQ443471:

Time Oxidized, Hrs co 1,200 Neutralization N 0.. 2. 0 2. 0

The above examples show the good oxidation stability imparted to mineral oil lubricant comp0- sitions by the use of our new addition agents. Mineral ,oil lubricant compositions containing our new addition agents are therefore eminently W ed for use where the operating conditions are extremely severe. as in Diesel, tank and truck engines, and in the lubrication of steam turbines.

The notable eflects of our new addition agents cannot be readily accounted for and cannot be predicted from the nature of the reactants. Thus. condensation products prepared from other functionally similarcompounds have been found to be either prooxidant or to show no antioxidant efiects whatsoever. For example, we have prepared condensation products similar to our new addition agents by substituting xylidine for the N-dimethylaniline. The resulting condensation products were found to be entirely unsuitable for inhibiting the oxidative deterioration of mineral oil lubricant compositions.

While we have shown in the examples the preparation of compounded lubricating oils, our invention is not limited thereto but comprises all mineral oil lubricant compositions containing our new addition agents, such as greases and the like. If desired, other known addition agents may be incorporated into the lubricant compositions prepared in accordance with our invention. For example, pour point depressants, extreme-pressure agents, viscosity index improvers and the like may be added.

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which comprises heating from 1 to 2 mols of dimethoxybenzaldehyde, 2 to 8 mols of N-dimethylaniline, and 2 to 8 mols of formaldehyde in the presence of an activated clay catalyst at a temperature not in excess of 350 F. to condense together the three reactants. and recovering the condensation product.

2. The process of preparing an addition agent For mineral oil lubricants which comprises heating 1 to 2 mols of dimethoxybenzaldehyde, 2 to 8 mols of N-dimethylaniline, and 2 to 8 mols of formaldehyde in the presence of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

3. The process of preparing an addition agent for mineral oil lubricants which comprises adding from 1 to 2 mols of dimethoxybenzaldehyde, 2 to 8 mols of N-dimethylaniline, 2 to 8 mols of formaldehyde and from 5 to 10 per cent by weight on the foregoing reactants of an activated clay catalyst to a mineral lubricating oil, heating the mixture at a temperature of from 150 to 300 F.

to condense together the three reactants, and rei covering a solution of the condensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of 2,3-dimethoxybenzaldehyde, 2 mols of N-dimethylaniline and 2 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation prodnet.

5. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of 2,3-dimethoxybenzaldehyde, 3 mols of N-dimethylaniline and 3 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

6. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of 2,3-dimethoxybenzaldehyde', 8 mols of N-dimethylaniline and 6 mols of formaldehyde in the presence of about 15 per cent by weight of an activated clay catalyst at a temperature from to 300 F. to condense together the three reactants, and recovering the condensation product.

- 7. A non-resinous condensation product of 1 to 2 mols oi dimethoxybenzaldehyde, 2 to 8 mols of N-dimethylaniline and 2 to 8 mols of formaldehyde, said' product being process of claim 1.

8. A non-resinous condensation product of 1 mol of 2,3-dimethoxybenzaldehyde, 2 mols of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process of claim 4. v

9. A non-resinous condensation product of 1 mol of 2,3-dimethoxybenzaldehyde, 3 mols of lfI-dimethylaniline and 3 mols of formaldehyde. said product being obtained by the process of claim 5.

10. A non-resinous condensation product of 1 mol oi 2,3-dimethoxybenzaldehyde. 3 mols of N-dimethylaniline and 6 mols of formaldehyde, said product being obtained by the process of claim 6.

11. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sui'ficient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 to 2 mols of dimethoxybenzaldehyde, 2 to 8 mols of N-dimethylaniline and 2 to 8 mols of formaldehyde, said product being obtained by the process of claim 1.

12. A lubricant composition comprising a major amount of a mineral lubricating oil, and a, minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a non-resinous condensation product of 1 to 2 mols of dimethoxybenzaldehyda'z to 8 mols of N-dimethylaniline, and 2 to 8 mols of formaldehyde, said product being obtained by the process of claim 2.

13. A lubricant composition comprising a. major amount of a mineral lubricating oil, and a minor amount, sufiicient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of 2,3-dimethoxybenzaldehyde, 2 mols of N-dimethylaniline, and 2 mols of formaldehyde, said product being obtained by the process of claim 4.

14. The composition of claim 16, wherein said condensation product is present in an amount of 0.5 per cent by weight.

15. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suflicient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of 2,3-dimethoxybenzaldehyde, 3 mols of N-dimethylaniline and 3 mols of formaldehyde, said product being obtained by the process of claim 5.

16. A lubricant composition comprising a major amount of a mineral lubricating oil and a minor amount, sufllcient to inhibit the oxidative deterioration of said oil, of a non-resinous condensation product of 1 mol of 2,3-dimethoxybenzaldehyde, 3 mols of N-dimethylanlline and 6 mols of formaldehyde, said product being obtained by the process of claim 6.

HERSCEEL G. SMITH. TROY L. CANI'RELL. JOHN G. PETERS.

(References on following page) obtained b the nu-mmcmscmm The following references are of record in flu file of this patent:

UNITED STATES PATENTS Number Name Date Regal May 11, 1928 Vacher ....1 Aug. 23, 1982 Mattiaon Apr. 10, 1934 Fuller Dec. 7, 1948 10 Number roman m'mu'rs Certificate of Correction Patent No. 2,513,063 June 27, 1950 HERSOHEL G. SMITH ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 44, for the claim reference numeral 2 read 1;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 19th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommissz'oner of Patents.

Certificate of Correction Patent No. 2,513,063 June 27, 1950 HERSCHEL G. SMITH ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 44, for the claim reference numeral 2 read 1;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 19th day of September, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTS WHICH COMPRISE HEATING FROM 1 TO 2 MOLS OF DIMETHOXYBENZALDEHYDE, 2 TO 8 MOLS OF N-DIMETHYLANILINE, AND 2 TO 8 MOLS OF FOMALDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGETHER THE THREE REACTANTS, AND RECOVERING THE CONDENSATION PRODUCT. 